1. Field of the Invention
The present invention relates to active matrix display devices which use current-driven luminescence elements represented by organic electroluminescence (EL) elements and to driving methods thereof, and more particularly to a display device having excellent power consumption reducing effect and to a driving method thereof.
2. Description of the Related Art
In general, the luminance of an organic electroluminescence (EL) element is dependent upon the drive current supplied to the element, and the luminance of the luminescence of the element increases in proportion to the drive current. Therefore, the power consumption of displays made up of organic EL elements is determined by the average of display luminance. Specifically, unlike liquid crystal displays, the power consumption of organic EL displays varies significantly depending on the displayed image.
For example, in an organic EL display, the highest power consumption is required when displaying an all-white image, whereas, in the case of a typical natural image, power consumption which is approximately 20 to 40% that for all-white is considered to be sufficient.
However, because power source circuit design and battery capacity entail designing which assumes the case where the power consumption of a display becomes highest, it is necessary to consider power consumption that is 3 to 4 times that for the typical natural image, and thus becoming a hindrance to the lowering of power consumption and the miniaturization of devices.
Consequently, there is conventionally proposed a technique which suppresses power consumption with practically no drop in display luminance by detecting the peak value of video data, and adjusting the cathode voltage of the organic EL elements based on such detected data so as to reduce power source voltage (for example, see Patent Reference 1: Japanese Unexamined Patent Application Publication No. 2006-065148).